1. Field of the Invention
The present invention relates to a method of recovering both silver and a base for sensitive materials, such as photofilms and photoprinting papers, by utilizing micro-organisms, and more specifically to a method of recovering them from sensitive materials, such as photofilms and printing papers, which have a gelatin membrane on their surfaces containing fine silver crystals.
2. Description of the Prior Art
No methods are known to exists wherein both silver and a reutilizable base can be recovered from photofilms or photoprinting papers.
Therefore, methods have been adopted that only silver is recovered by incinerating photofilms or photoprinting papers. But these, methods have the problems of public nuisance, because the generation of offensive odor and dust will occur in disposing of the incinerated materials, and many chemical agents and processes are required in order to separate a pure silver from ashes, because ashes and silver are mixed in photofilms or photoprinting papers. There was another method of recovering silver from the surface of photofilms, in which a high concentration of sodium hydroxide was employed. In this method it was impossible to separate only silver by filtration, etc., because it was accompanied by an alkaline drainage, and several kinds of additives were mixed in gelatin membranes on the film to increase the efficiency of the films. Further, the recovery of a film base is impossible in this method.
On the other hand, the amount of such sensitive materials as used photofilms and photoprinting papers which should be disposed of, both for industrial and domestic uses, has recently increased. The surface of these films have gelatin membranes containing fine silver crystals. If silver and a reusable film were able to be recoverd from these sensitive materials which should be disposed of, it would be much advantageous to a sparing of resources or a countermeasure for public nuisance.